refactor(core): move facades out of core

This is part of ongoing work to make core platform-independent.

BREAKING CHANGE

All private exports from 'angular2/src/core/facade/{lang,collection,exception_handler}' should be replaced with 'angular2/src/facade/{lang,collection,exception_handler}'.

modules/angular2/src/http/base_request_options.ts

@@ -1,4 +1,4 @@
-import {isPresent, isString} from 'angular2/src/core/facade/lang';
+import {isPresent, isString} from 'angular2/src/facade/lang';
 import {Headers} from './headers';
 import {RequestMethods} from './enums';
 import {RequestOptionsArgs} from './interfaces';